A to B
Say what you know. Say what you want.
It searches a graph of physics relations for a chain of substitutions that connects the two, and shows every step — the formula, the numbers going in, the value coming out.
The corpus
Two hundred and eleven relations, and every symbol typed.
Mechanics through astrophysics. Every symbol in every formula carries a base dimension, which is what makes the checking below possible at all rather than decorative.
The check
Both sides reduce to the same thing, or it says so.
Every relation is reduced to mass, length, time, current, temperature, amount and light. A term added to another of a different kind is the most common way to be wrong, and it is the one thing arithmetic alone will never catch.
When there is no path
It tells you the search failed.
Most tools of this kind quietly produce something anyway. This one stops, says so, and only then offers to ask a language model for a relation that would connect them.
And then it checks that too
Verified, refused, or honestly unverified.
A proposal is dimension-checked and evaluated against the known formulas before you read it. One that fails is refused. One that could not be checked says exactly which check could not run. There is no fourth state where the tool hopes for the best.